Ketoconazole-resistant mutants of Microsporum gypseum. I. Isolation of mutants, biochemical methods.

The ketoconazole-resistant mutants were isolated from four strains of the dermatophyte Microsporum gypseum. The frequency of spontaneous mutants ranged within 10(-8) to 10(-9) (per spore and nucleus). The method was established for obtaining the spontaneous mutants manifested as the faster growing sectors. By means of mutagenic effect of UV radiation, the frequency of mutants increased by one order. The method used for determination of ergosterol the biosynthesis of which could be associated with the mechanism of resistance to ketoconazole is described and evaluated.